Power Steering Questions

" Kimi's driving style requires plenty of steering feedback. He's very adaptive to changes in grip, has a great instinctual feel for where it is as the track changes and the tyres degrade. But that feedback to the wheel in these days of power steering - necessary because of the high degree of camber thrust teams use to speed up the initial turn of the car - is not always an easy thing to deliver, and for much of the season so far Raikkonen has kept the team busy designing and making new components in the search for the feedback he wants. Coming into the Monaco weekend - the track with the tightest corners on the calendar and therefore the one requiring the greatest amount of steering lock - Kimi had further requested a high-ratio steering system, giving greater lock for a given degree of steering wheel input.
The Enstone guys readily agreed, even though designing and manufacturing such a system is a time-consuming business. It drained factory engineering effort away from a lot of other projects for around three weeks. As has been well-reported, Kimi made a single out-lap in Thursday morning practice at Monaco, came in, declared that the car was undriveable with this steering, almost totally devoid of feedback.
Re-fitting the conventional system is a 1.5-hour job and he was asked to consider running the session with it as it was, so that the standard system could be fitted in between sessions. He refused and took no further part in that session - the only one in which extended dry track running could have been made, as it turned out. With the afternoon session rained out, the team was sorely bereft of useful tyre data.
Producing a power steering system that combines good feedback with a high ratio is an exceptionally difficult thing to do. To give good feel, the steering must lighten noticeably as the grip reduces and weigh-up again as it increases. It must do this almost instantaneously. But that varying load has to be transferred from various torsion bars, through the medium of hydraulic fluid working on hydraulic rams. There is an inevitable inertia in the system - and the higher the steering ratio, the less finely-honed those varying degrees of resistance can be. Kimi felt that to continue the session around the streets of Monaco with the steering so dead-feeling was to invite hitting the wall. "

QUESTIONS

(1) What is camber thrust and how does it help turn in ? And how come this requires power steering to be used ?

(2) Does high ratio system require power steering automatically compared to lower gear ratio which should be easier for the driver to turn ?

(3) Does anybody know what controls the feedback of the system ?

(4) Finally why does steering lighten with grip and weigh up ( what does "weigh - up" mean) when grip increases ?

Many thanks to everybody reading my question. I'm studying electrical engineering so I have limited knowledge of mechanical systems.

(1) What is camber thrust and how does it help turn in ? And how come this requires power steering to be used ?

(2) Does high ratio system require power steering automatically compared to lower gear ratio which should be easier for the driver to turn ?

(3) Does anybody know what controls the feedback of the system ?

(4) Finally why does steering lighten with grip and weigh up ( what does "weigh - up" mean) when grip increases ?

Many thanks to everybody reading my question. I'm studying electrical engineering so I have limited knowledge of mechanical systems.

1) if you lean the tire over it generates a side force. That is camber thrust. It doesn't need PAS. If you mess about with the steering geometry (lots of KPI and static camber) then you jack the car up as you turn the wheels, which is probably what they mean)2) Typically you can double the gear ratio if you go to assisted steering on a street car. (3 turns lock to lock not 5 or so). 3)In a conventional HPAS the feedback is provided by the boost curve which does not, on most cars, provide 100% assistance. There are exceptions. So some (not necessarily fixed) proportion of the force in the rack is felt by the driver. EPAS works similarly.4)Because the side force generated by the tire moves longitudinally. At low levels of sideforce for a given surface it is a long way behind the centre of the tire and then moves forward as the grip increases. This changes the moment of the force about the kingpin, so even though the force is increasing towards saturation, its moment reduces overall, giving the lightening off feeling. This can be tuned via the mechanical trail.

I was told a couple years ago that the power steering accounts for about 80% of the steering force on F1 cars (the driver provides the rest) with some sort of curve on the input vs. output. I believe it has to be all mechanical to prevent computer-assisted steering. Anyway, I assume it's this curve that Kimi wants tuned differently. IIRC, Trulli had some similar issue last year.

I now see Greg has answered this better and more completely. I'm curious about the "100% assistance" - wouldn't that mean the driver basically feels nothing? I actually have a vacuum (I'm talking about the household cleaning instrument here) that automatically propels it in the direction it's going. The feature feels bizarre, it takes no effort to do a large open space but it's almost impossible to stop just before hitting the wall. Luckily you can turn it off. My point here, now that I've derailed, is that something close to 100% assistance would be difficult to control accurately.

On a road car an EPAS can provide around 10 times what a human regards as a comfortable steering wheel torque.

Yes 100% assistance would feel odd. Citreon have used it in the past, the only 'feel' was a spring. However not all of your control is via steering wheel torque. There are circumstances in which you get more than 100% assistance (ie SWT vs SW velocity goes negative), even on an HPAS, and they are troublesome. If you notice your EPAS 'motoring' the steering wheel then it is disconcerting.

Many thanks to Greg Locock. I really appreciate it. What book do you recommend to learn more about power steering ? I'm especially confused about how the torsion bar figures out which hydraulic ports to open and close thereby setting the direction in which assistance is provided (basically how does the system

figure out you are turning left and then it provides assistance in the correct direction) ?? I'm also interested in learning about this boost curve and how it is derived.

I'm also interested in learning about this boost curve and how it is derived.

Basically with HPAS you drive the car, and then think, hmm that feels a bit non linear there, or too light or too heavy, and so you try and modify that bit of the curve without stuffing anything else up. With HPAS your options are limited, the curve of assistance versus demand can only be one shape (basically between U and V shaped), you are tuning the degree of curvature and when it starts. And T bar stiffness. If you have velocity sensitive assistance that makes things slightly more complicated, as you have more knobs to twist, but easier, because the compromises are fewer.

With epas the world is your oyster. Since we know what we want as an outcome it is just a case of messing about with some tables. I can do the base cal (assist vs demand vs speed) in ADAMS, all the fine tuning is done in the car. Again the shape of the curves is fairly fixed (by what humans expect), in fact some manufacturers parametise the curves, we don't, we enter numbers into tables.

I would think that the steering wheel feedback is one of the hardest things to get right because of the shape of the steering wheel rim load curve.

If I have it right the driver has two non-visual inputs into maximum lateral G achievement.

- the sensing of lateral G in the balance tubes of the ear

- The steering wheel load feedback

The problem is that as the tyre slip angle and so maximum lateral force is reached the steering wheel load reduces because the pneumatic tiail falls off as the rear of the break away zone comes forward.

So the drivers brain senses both lateral G climbing and wheel rim load climbing, then the signals suddenly diverge and the driver has to sense very small cahnges in rim force as the self aligning torque curve goes flat.

I guess the skill of a top driver partially lies in his/her abilty to sense the reversal and the very slight changes at the top of the self aligning curve ( a bit like sensing when the piston is at TDC with a probe through the plug hole or not over tightening a bolt).

What I don't understand is whether the design of a racecar steering load is a fundementally different requirement to a road car since very, very few road drivers ever get to the flat point on the self aligning curve.

I would think that the steering wheel feedback is one of the hardest things to get right

The steering feel question is fascinating. It does seem that many of the (road) cars that inspire the greatest affection are those that have a reputation for fine steering (early 911, mini, Elan, etc) The design of a steering servo must add considerably to the difficulties of keeping good steering feel but steering 'weight' is only a little part of it. The road cars we drive all are compromised differently; in favour of light or numb, quick or "safe" steering. Is there any contemporary car that excels for steering feel (despite it's low profile tyres / front wheel drive / power assistance)?

And by the way, a big thank you to Greg Locock for his time taken to share wisdom in many posts here and elsewhere .

What I don't understand is whether the design of a racecar steering load is a fundementally different requirement to a road car since very, very few road drivers ever get to the flat point on the self aligning curve.

The bolt comparison is excellent. Yes i don't know whether racecars are different, one would guess they are more linear. In every car company I have worked for the handling at the limit /is/ assessed, for instance one competitor has an issue if you 'saw' the wheel in a 0.7g corner, with SWTorque and velocity getting out of phase, so we look for that.

BMW was the gold standard for many until EPAS. More recently, Mazda, Cadillac, and Porsche seem to draw praise from all around.

To be honest it's a rather personal and subjective thing. (<-- EDIT: *can often be*) Also, what people call steering feel might encompass a number of items. For example, the current Mustang probably has good steering feel but for all the wobbly bits it's bolted to.

As Greg has said " the world is your oyster with EPAS" I have an idea for road cars to help drivers who are not Vettel etc.

Asuming the car with EPAS also has automatic Stabilty Control (ASC) it wil have lateral accelerometers. So you write a algorithm which is only activated at high lateral G.

The algorithm compares the rate of change in the steering rack load from the wheels to the force from the driver on the steering wheel rim. If it detects that the wheel load is dropping rapidly versus driver load ( i.e the self aligning torque curve is flattening out) tthe algorithm sends signals to the EPAS motor.

The signals generate a rapid but very small amplitude vibration at the steering wheel rim. This is clear signal to the driver that he/she has reached the limit of adhesion. It should be a much clearer message than the subtle signals from the self aligning torque curve.

You could even link it to the screen wipers to trigger at lower G if it is ( by implication ) raining.

It's basically a version of an aircraft " stick shaker" used to warn of an impending stall condition.

I have yet to drive ANY EPAS car which has straight line steering feel superior to a good HPAS (or presumably manual but that was a long time ago) setup, mainly it feels dead or lots of friction. BMW in particular have gone from class leader (or thereabouts) in every vehicle segment, for steering feel, to a general sort of 'what the hell were they thinking' level, still better than average, but no longer the obvious image vehicle. Rather like Mercedes did with quality 15 or 20 years ago. That could be a conscious decision, it could be an outcome of two technologies they've introduced (run flats and their EPAS). They occasionally go on record saying they don't rely on measurements, so they may not even know they've gone weird.

The problem with EPAS is that you have a tiny little motor and a great big ratio gearbox, which provide an inertia and friction and damping that is more or less additional to everything you have in an HPAS. The cluey companies provide electrical compensation for this - and it does help. But if you apply too much extra electrical oomph to overcome these forces, then the system starts to feel like it is motoring, which is disconcerting.

pbukovca;in case you missed this in the responses,three things will make steering heavy--wide tyres,static negative camber and positive caster settings..all of which are necessary for good grip.The positive caster is there to cause the wheel with the weight on it--the outside wheel on a turn--to generate increasing negative camber as more lock is applied.Have a look at most cars when they happen to be parked on full lock.Tighter circuits bring advantage with this setting.The downside of the positive caster is when you turn in you are in effect jacking up the car on the weight bearing side a little when you apply lock ,and power assistance becomes a necessity.Kimi wanted faster ratio steering for tighter corners,so more power assistance is needed...but this of course means less remaining feedback to the driver,as his own arm muscles,and hand grip, have less involvement. One would think all drivers would need what Kimi needed,they
all drive on feel.Probably are other related issues.It does not appear any F1 drivers move their hands very far when steering to begin with.

Side Question--does aero downforce on the front make steering heavier ?

In our family are two Fiat Panda's - one a 1986 with 155/13 tyres and manual steering. It weighs about 750kg and has 45 bhp

The other is a 2007 model with 195/14 tyres and EPAS. It weighs about 1000kg and 100bhp.

The steering difference is amazing, the older car is heavier at manoveuring speed but very light on the road and "soft but instant" in response.

The newer one has lighter steering at very low speeds and is "firm but inert" in feel. It has a "sport" setting which reduces power boost so you an feel sporty (!). the only use I have found is on long motorway jouneys where the sport setting reduces your reaction to cross winds a bit - otherwise a waste of time.

Thats not any great news but where the two cars REALLY show a difference is on snow. The older one is just so much more sure footed and easier to keep moving. Part of it is less power but the combination of lower inertia and manual steering plus thinner tyes makes the old one our best car for the snowfalls we do get nowadays in southern Uk.

My son enjoyed passing all the local BMW 3 series company car drivers up our local hill in the 26 yr old Panda last year! - horses for courses

The road cars we drive all are compromised differently; in favour of light or numb, quick or "safe" steering. Is there any contemporary car that excels for steering feel (despite it's low profile tyres / front wheel drive / power assistance)?

My VW Jetta has excellent steering feel, even though it's electrical power steering. It hits the sweet spot of not being hard to steer, but still giving clear communication. Of course, unless you drive like an idiot, you only really get to feel it when you're driving on the snow or similarly slippery conditions. VW in general has a reputation for good steering feel, AFAIK. I've driven BMWs, and I'm not impressed. Maybe I'm not used to it, but it makes me feel like I'm in a gym working on my arm muscle tone.

Many thanks to Greg Locock. I really appreciate it. What book do you recommend to learn more about power steering ? I'm especially confused about how the torsion bar figures out which hydraulic ports to open and close thereby setting the direction in which assistance is provided (basically how does the system

figure out you are turning left and then it provides assistance in the correct direction) ?? I'm also interested in learning about this boost curve and how it is derived.

Again many thanks to all.

Not sure about the specifics of the Lotus pas but typical F1 systems use a flexure to position the pinion within the rack housing. As the torque on the pinion increases the pinion deflects against the flexure stiffness. This movement of the pinion is transferred to a Moog valve which controls the hydraulic pistons in series with the rack and hence the amount of assistance.

I can tell you one that doesn't - unless my wife's sample is a rogue - the Honda Jazz. I have never known a more disagreable car to steer, or keep in a straight line.

Well, possibly your wife has chosen a rogue. Ours is boring/dull but very good at it's job. Try 38 F & R for better tyre wear.

This has probably been covered before but most people have no idea if their car has PAS and don't really care. The only time it ever gets mentioned is in terms of some strange noise or a heavy/disconnected feeling. Warning lights are often ignored as long as the car keeps going.

In our family are two Fiat Panda's - one a 1986 with 155/13 tyres and manual steering. It weighs about 750kg and has 45 bhp

The other is a 2007 model with 195/14 tyres and EPAS. It weighs about 1000kg and 100bhp.

The steering difference is amazing, the older car is heavier at manoveuring speed but very light on the road and "soft but instant" in response.

The newer one has lighter steering at very low speeds and is "firm but inert" in feel. It has a "sport" setting which reduces power boost so you an feel sporty (!). the only use I have found is on long motorway jouneys where the sport setting reduces your reaction to cross winds a bit - otherwise a waste of time.

Thats not any great news but where the two cars REALLY show a difference is on snow. The older one is just so much more sure footed and easier to keep moving. Part of it is less power but the combination of lower inertia and manual steering plus thinner tyes makes the old one our best car for the snowfalls we do get nowadays in southern Uk.

My son enjoyed passing all the local BMW 3 series company car drivers up our local hill in the 26 yr old Panda last year! - horses for courses

Ye ! bring on the Classic Pandas

I have a '86 model I use for Car Trials [twice Cotswold PCT champion in it ]

The switch on the EPAS for the Panda was referred to as the girlie switch by the development engineers. They logged where people used it and which position they left it in...and discovered that the sports calibration was virtually unused. Much the same happens with the manual overrides for auto boxes, people play with them a bit at first but by and large stick the thing in D most of the time. Well I've heard Tony prefers to drive around in R, but that's just attention seeking behaviour. An exception to that is on the 4 speed BTRE box, where 3 put you into direct drive, locked up, which was a real economy and transmission saver if towing.

It may come as a shock but there are misguided people out there that are fitting EPAS to their old Minis.

I am afraid I have to disagree somewhat - I think EPAS on a Mini might be a good idea. I drove Minis for 20 years (including some racing) and I always thought that the steering ratio needed to be a bit quicker to match the very short wheelbase. But the Mini steering was pretty heavy as it was (especially with widish tyres) and a quicker ratio would have made it too heavy. I would like to know just what EPAS is fitted to old Minis.

4)Because the side force generated by the tire moves longitudinally. At low levels of sideforce for a given surface it is a long way behind the centre of the tire and then moves forward as the grip increases. This changes the moment of the force about the kingpin, so even though the force is increasing towards saturation, its moment reduces overall, giving the lightening off feeling. This can be tuned via the mechanical trail.

I thought this was a very interesting explanation of tyre grip/feel through the sreering. But wouldn't the "feel" be equally dependent on the coefficient of friction between the tyre and the road? Clearly on wet grass, gravel, wet smooth concrete etc. it is much easier to turn the steering wheel in a stationary car rather than on a good, dry tar surface. When the tyre approaches its grip limit on a good surface wouldn't the COF drop giving the "lightening-off" steering feel?

Not sure about the specifics of the Lotus pas but typical F1 systems use a flexure to position the pinion within the rack housing. As the torque on the pinion increases the pinion deflects against the flexure stiffness. This movement of the pinion is transferred to a Moog valve which controls the hydraulic pistons in series with the rack and hence the amount of assistance.

Don't most road-going HPAS systems use a "flexure"/flexible shaft in a similar fashion?

That's the stupidest thing I ever heard. Unless the person has a physical disability it make no sense at all.

It is just a stupid kid thing. New cars have EPAS so therefore their car should have it.They also throw out the rubber springs and fit poorly designed coil springs or coil-overs that fit on the shock mounts (and then break the shock mounts!).

Well, possibly your wife has chosen a rogue. Ours is boring/dull but very good at it's job. Try 38 F & R for better tyre wear.

I don't mind my wife having a dull, boring car, as I don't expect to drive it often, but when I do, the steering is what I dislike (plus the Teflon  steering wheel). It is at its worst on the straight as the constant tiny adjustments that I instinctively, unconciously make give me pain in the forearms and wrists. Happens every time, and starts after about 30 mins.

Well I've heard Tony prefers to drive around in R, but that's just attention seeking behaviour.

I've re-read the thread and can't see another Tone, so perhaps this is me! Actually, apart from California '94 and a one-way drive to Silverstone about 6 years ago, the only time I've done a substantial amount od driving with an auto box was in the very late '60s, early '70s, towing a Formula Ford around Europe for a total of several months, using a Jaguar Mk 9. I'm not a fan of auto boxes, although I have no trouble adapting - apart from left-foot braking...

Tony, a Honda Jazz is a disagreeable piece of mechanised transport. It is not a car!

I thought this was a very interesting explanation of tyre grip/feel through the sreering. But wouldn't the "feel" be equally dependent on the coefficient of friction between the tyre and the road? Clearly on wet grass, gravel, wet smooth concrete etc. it is much easier to turn the steering wheel in a stationary car rather than on a good, dry tar surface. When the tyre approaches its grip limit on a good surface wouldn't the COF drop giving the "lightening-off" steering feel?

As I understand it the COF and the self aligning torque are directly related via the slip angle.

Basically as the tire footprint is turned versus straight ahead ( the slip angle) distortion occours in the contact patch which is what generates the cornering thrust. More slip angle means more distortion means more lateral force i.e grip. However the distortion generates a shearing force to get the tyre face back to its unstressed position when it is unloaded leaving the contact patch.

As the biggest distortion is at the rear of the tyre it shears first so the effective length of the contact patch shortens as slip angle increases and the self aligning torque reduces ( because the centre point of the distorted contact patch area is moving forward.

I hope I have done tyres 101 right!

So , logically less COF means less fall off in self aligning torque as less of the "tearing" ocours.

This implies that it should be easier to sense the limit in the wet than the dry because you don't have to sense the fall off in the self aligning torque so much but history suggests that the most sensitive drivers ( Clark, Senna etc) do even better in the wet which is an interesting point to discuss??

... the steering is what I dislike (plus the Teflon  steering wheel). It is at its worst on the straight as the constant tiny adjustments that I instinctively, unconciously make give me pain in the forearms and wrists. Happens every time, and starts after about 30 mins.

A quick google shows you are not alone with this. Possibly a recalibration needed or an alignment problem. Has your friendly local dealer had a look? I'll make some more checks.

My wife has an 2004 Honda Civic and it has exhausting electric power steering: from the neutral position there is an initial stiffness completely at odds with the low additional angular force required to increase yaw. This is tiring all the time and lets down an otherwise satisfactory and spectacularly reliable transport appliance.

Too much emphasis is placed on extremes of behavior with steering: extreme light weight for parking and on-the-limits-of-grip behavior.

Steering feel is important because steering is the control that is in use all of the time that the vehicle is in motion. I think that it is second only to seat / driving position comfort in fatigue significance. My own car, a Toyota MR2 roadster has hydraulic power-steering. There is normally no feedback at all through the steering wheel rim, it is completely numb. At the limit of front end grip (only approached in my road driving in low speed / tight radius situations) I get more information from the squealing sounds of the front tyres. Why does a tiny car like an MR2 have steering heavy enough to require power assistance? 185 front tyres each carrying about 250kg - ridiculous. The steering is too heavy without the assistance (Easy to disable, hydraulic but with an electric pump) but why?

Wind the clock back 30 years or so to my Morris Minor: a poor car in many ways but the steering, on it's set of 155 steel radials, was always a pleasure; light enough, informative and utterly trustworthy.

My wife has an 2004 Honda Civic and it has exhausting electric power steering: from the neutral position there is an initial stiffness completely at odds with the low additional angular force required to increase yaw. This is tiring all the time and lets down an otherwise satisfactory and spectacularly reliable transport appliance.

Too much emphasis is placed on extremes of behavior with steering: extreme light weight for parking and on-the-limits-of-grip behavior.

Steering feel is important because steering is the control that is in use all of the time that the vehicle is in motion. I think that it is second only to seat / driving position comfort in fatigue significance. My own car, a Toyota MR2 roadster has hydraulic power-steering. There is normally no feedback at all through the steering wheel rim, it is completely numb. At the limit of front end grip (only approached in my road driving in low speed / tight radius situations) I get more information from the squealing sounds of the front tyres. Why does a tiny car like an MR2 have steering heavy enough to require power assistance? 185 front tyres each carrying about 250kg - ridiculous. The steering is too heavy without the assistance (Easy to disable, hydraulic but with an electric pump) but why?

Wind the clock back 30 years or so to my Morris Minor: a poor car in many ways but the steering, on it's set of 155 steel radials, was always a pleasure; light enough, informative and utterly trustworthy.

A lot more caster on modern cars which generally makes them a lot heavier to steer.And everybody has to have power steering wether the car needs it or not.Strangely the Sports Sedan I used to race was lighter than the standard sports model of the car to steer. Even with 10" wide rims, 290mm wide tyres with 6deg of caster and 3+ camber!!

I don't mind my wife having a dull, boring car, as I don't expect to drive it often, but when I do, the steering is what I dislike (plus the Teflon  steering wheel). It is at its worst on the straight as the constant tiny adjustments that I instinctively, unconciously make give me pain in the forearms and wrists. Happens every time, and starts after about 30 mins.

I've re-read the thread and can't see another Tone, so perhaps this is me! Actually, apart from California '94 and a one-way drive to Silverstone about 6 years ago, the only time I've done a substantial amount od driving with an auto box was in the very late '60s, early '70s, towing a Formula Ford around Europe for a total of several months, using a Jaguar Mk 9. I'm not a fan of auto boxes, although I have no trouble adapting - apart from left-foot braking...

Part of me agrees, Lee, but the Vauxhall Corsa is worse...

Tony, most FWD small shopping trolleys are mechanised transport, as are gophers and electric wheel chairs! They all go from A-B but are as exciting as watching grass grow. Toyota make more than their fair share of them too.

Tony, it might be an optical illusion or an optical effect from the camera lens being used, but the car looks like it has some toe out on that rear wheel. Toe out in the rear will make almost any car 'squirrelly'.

In my day job training technicians, it's a never ending task to ensure they calibrate the steering angle sensor for the EPAS and the ESP every time they touch the front suspension or steering and that includes work on the back of the car. Most small cars have a twist beam rear axle these days and if that is shifted then the tracking gets askew and apart from the mechanical alignment necessary, the computers need to be shown where the 'null point' is.

Tony, most FWD small shopping trolleys are mechanised transport, as are gophers and electric wheel chairs! They all go from A-B but are as exciting as watching grass grow.

I realise that, Lee, I knew I wasn't going to drive it often so I didn't push for the GTR.

Tony, it might be an optical illusion or an optical effect from the camera lens being used, but the car looks like it has some toe out on that rear wheel. Toe out in the rear will make almost any car 'squirrelly'.

Thanks Pat, I think it is the focal length of the lens and my proximity to the car - a bit of parabolic perspective creeping in. The car was never squirrely, before or after, just dead steering at straight ahead. However, I'll keep a check on tyre wear, and may have the geometry checked. It's not apparent in this shot, but a wheel was broken and the sump cracked too. Bastards.

"In my day job training technicians, it's a never ending task to ensure they calibrate the steering angle sensor for the EPAS and the ESP every time they touch the front suspension or steering and that includes work on the back of the car. Most small cars have a twist beam rear axle these days and if that is shifted then the tracking gets askew and apart from the mechanical alignment necessary, the computers need to be shown where the 'null point' is."

Pat, I had never even though about this problem. One of my cars has EPAS and the other has hydraulic steering but full ESP.

Many cars sold in the EU wil have EPAS and ESP is soon to be mandatory on all new cars in the EU.

It seems to my old fashioned brain that its another example of technology allowing legistlation which combined run too far ahead of reality.

I can see why you might want to reset the null point but how critical is it? Ideally every car should get a full 4 wheel alignment to set the thrust line right but I don't think many do. A lot of UK fast fit operators don't even have 4 wheel alignment gear. It sounds like only OEM dealers could do suspension work under your scenario.

Now of course I could pretend to be in California and the car swerves off the road and crashes. If I can't pin it on the mfgr but found it had ben re-tracked without resting the null point I could sue the fast fit chain that did the work could I not??

Having sent the terrible workmanship of one of the UK's biggest fast fit chains on family cars I am tempted to phone them and ask how they will reset the EPAS or ASC after a job!!

Many cars sold in the EU wil have EPAS and ESP is soon to be mandatory on all new cars in the EU.

It seems to my old fashioned brain that its another example of technology allowing legistlation which combined run too far ahead of reality.

There's a reasonable amount of statistics in favour of ESC, primarily from the USA, primarily because it helps to stop people rolling their SUVs and trucks by doing inappropriate things with the steering wheel. I don't have a problem with traction control, ABS or ESC or ROP or any of these other funny systems, so long as they can be disabled if I don't want them. That is not the case with ABS, nowadays, and in effect you always get 'some' ESC or ROP even if you switch them off on the dashboard with many cars. Thinking about it you may not even be able to switch TC off completely, there's always some driveline protection issues. It would be interesting, if impossible, to find out how many cars develop full torque in first gear these days, particularly sporty ones!